Patent reference 1 discloses a production method of a 4-oxoquinoline compound represented by the formula [II]:
wherein each symbol is as defined in patent reference 1 (hereinafter sometimes to be abbreviated as compound [II]). Specifically, the following production methods are known.Production Method 1-1 (See Patent Reference 1: Page 67)

Each symbol in the scheme is as defined in patent reference 1.
This production method is also described in patent reference 2, page 64 (each symbol in the scheme is also defined in patent reference 2).
Production Method 1-2 Example of Production Method Using Compound [9], into which Hydroxyl-Protecting Group has Been Introduced (See Patent Reference 1: Page 71)

Each symbol in the scheme is as defined in patent reference 1.
This production method is also described in patent reference 2, page 68 (each symbol in the scheme is also defined in patent reference 2).
Production Method 2-1 (See Patent Reference 1: Page 72)

Each symbol in the scheme is as defined in patent reference 1.
This production method is also described in patent reference 2, page 69 (each symbol in the scheme is also defined in patent reference 2).
Production Method 2-2 Example of Production Method Including Introduction-Deprotection Step of Hydroxyl-Protecting Group (See Patent Reference 1: Page 74)

Each symbol in the scheme is as defined in patent reference 1.
This production method is also described in patent reference 2, page 72 (each symbol in the scheme is also defined in patent reference 2).
Production Method 3 (See Patent Reference 1: Page 76)

Each symbol in the scheme is as defined in patent reference 1.
This production method is also described in patent reference 2, page 74 (each symbol in the scheme is also defined in patent reference 2).
Production Method 4 (See Patent Reference 1: Page 77)
Examples of the production methods of the above-mentioned compound [12] are specifically shown in the following.

Each symbol in the scheme is as defined in patent reference 1.
Production Method 5 (See Patent Reference 1: Page 79)

Each symbol in the scheme is as defined in patent reference 1.
This production method is also described in patent reference 2, page 78 (each symbol in the scheme is also defined in patent reference 2).
The above-mentioned production method 1-1 and production method 2-1 relate to production methods of compound [1-2] and compound [1-5], respectively, which correspond to the above-mentioned compound [II].
In production method 1-2, production method 2-2 and production method 5, examples of production via introduction deprotection of a hydroxyl-protecting group are shown.
In addition, production method 3 discloses a method of introducing a substituent after 4-oxoquinoline ring formation, and production method 4 describes example of a more specific production method of compound [12].
In addition, patent reference 1 discloses, of compound [II], 6-(3-chloro-2-fluorobenzyl)-1-((S)-1-hydroxymethyl-2-methylpropyl)-7-methoxy-4-oxo-1,4-dihydroquinoline)-3-carboxylic acid (hereinafter sometimes to be abbreviated as compound (10)) as one of the compounds particularly useful as an anti-HIV agent, and a production method thereof.
Specifically, Example 4-32 of patent reference 1 describes the following production example.
In addition, production of 2,4-difluoro-5-iodobenzoic acid, which is a starting material, is disclosed in patent reference 1, Example 4-33, step 1.
wherein NIS is N-iodosuccinimide, catalyst shows a catalyst, and other symbols are as defined in patent reference 1.
This production method is also described in patent reference 2, page 112, Reference Example 9.
As a production method similar to this production method, patent reference 3, page 23, Example 2-1 describes a production method wherein the hydroxyl-protecting group is a tert-butyl dimethylsilyl group. In addition, patent reference 3, page 12, Reference Example 1; page 17, Example 1 and page 39 and Example 2-4 describe a method of directly producing compound (10) from a compound wherein the hydroxyl-protecting group is a tert-butyldimethylsilyl group.

Moreover, patent reference 1, page 81, Reference Example 1, and patent reference 2, page 80 or Reference Example 1 disclose that 2,3-dichlorobenzylzinc chloride which is an analog of 3-chloro-2-fluorobenzylzinc bromide produced in the above-mentioned step 6 can be produced in the same manner from 2,3-dichlorobenzyl chloride.

Patent reference 3 discloses a production method of compound (10).
Specifically, patent reference 3, Example 2-2, page 28 describes the following production example.
wherein DBU is 1,8-diazabicyclo[5.4.0]undecene, catalyst shows a catalyst, and other symbols are as defined in patent reference 3.
Patent reference 1, patent reference 2 and patent reference 3 disclose production methods of compound (10). The references have the following aspects.
In the final step (alkoxylation, particularly methoxylation), a dimer is by-produced depending on the base to be used. Thus, in this event, a removal step of the by-produced dimmer is further necessary, which decreases the yield greatly.
When sodium fluoride by-produced in the final step (alkoxylation, particularly methoxylation) is acidified in the treatment step, hydrofluoric acid is produced, which corrodes the production facility. Thus, a removal operation of sodium fluoride is essential and the operation is complicated.
There is a concern about an unfavorable influence of hydrofluoric acid produced in the ring-closing step on the production facility, and therefore, the method is not of a level satisfactory as an industrial production method.
Removal of the product by-produced in a reaction to insert compound [IIb] is complicated (since alkyl zinc derivative is used with a palladium catalyst, an operation to remove zinc salt and palladium salt as impurities is necessary and the operation is complicated).
Plural operations are necessary to protect hydroxyl group with methyl chloroformate in a preliminary step of the reaction to insert compound [IIb], and to deprotect the group in a later step, and the operation is complicated.
A step using 3-chloro-2-fluorobenzyl bromide for the production of compound [IIb] is not beneficial for industrial production since the compound shows high tearing property.
The above-mentioned production methods including these steps are associated with many aspects to be improved for industrial production, and the development of a more superior production method of compound (10) is desired.
In addition, while non-patent reference 1 describes the following 4-oxoquinoline compound and the like, the compounds (8) and (9) of the present invention, which are explained in detail in the following, are not described.

In addition, while Example 1 (1c) of patent reference 4 describes the following acrylic acid ester and the like, the compounds (6) {(6-A) and (6-B)}, and (7-1) of the present invention, which are explained in detail in the following, are not described.

Moreover, patent reference 5 describes a production example of 4-oxoquinoline skeleton from the following acrylic acid ester and the like, in a ring-closing reaction during formation of 4-oxoquinoline skeleton. However, a production method from compound (7-1) to compound (8) and a production method from compound (6-B) to compound (7-2) like those in the present invention explained in detail in the following are not described.

[Patent reference 1] WO 04/046115
[Patent reference 2] WO 05/113509
[Patent reference 3] WO 05/113508
[Patent reference 4] WO 03/043992 (page 195, line 10)
[Patent reference 5] U.S. Pat. No. 4,695,646 (column 15, line 40)
[Non-patent reference 1] Folia Microbiologica, vol. 19, number 4, pages 281-291, 1974 (page 282, FIG. 1)